To provide cellular wireless communication service, a wireless service provider typically operates a radio access network (RAN) that defines one or more wireless coverage areas in which access terminals (ATs) can be served by the RAN and can thereby obtain connectivity to broader networks such as the public switched telephone network (PSTN) and the Internet.
A typical RAN may include one or more base transceiver stations (BTSs) (e.g., macro network cell towers and/or femtocells), each of which may radiate to define a wireless coverage areas such as cells and cell sectors in which ATs can operate. Further, the RAN may include one or more base station controllers (BSCs) or the like, which may be integrated with or otherwise in communication with the BTSs, and which may include or be in communication with a switch or gateway that provides connectivity with one or more transport networks. Conveniently with this arrangement, an AT that is positioned within coverage of the RAN can then communicate with a BTS and in turn, via the BTS, with other served devices or with other entities on the transport network.
In general, a RAN will communicate with an AT according to an agreed air interface protocol, examples of which include CDMA, iDEN, WiMAX, LTE, TDMA, AMPS, GSM, GPRS, UMTS, or EDGE, and others now known or later developed. The air interface protocol will define a mechanism to distinguish communications in one coverage area from those in adjacent coverage areas and to distinguish between communications within a given coverage area. For instance, under the CDMA protocol, each sector has a unique “PN offset” that is used to encode communications carried out in the sector in a manner that distinguishes communications carried in adjacent sectors. Further, each sector defines various control channels and traffic channels, each encoded with a respective “Walsh code.” Other examples are possible as well.
A RAN will typically broadcast a pilot signal or the like respectively in each coverage area, to enable user devices to detect and evaluate cellular coverage in that area. For instance, when a user device is operating on an assigned traffic channel in a given coverage area, the user device may regularly monitor the strength of the pilot signal in that coverage area and may likewise monitor the strength of pilot signals that may come from nearby coverage areas. If the pilot signal from an adjacent coverage area becomes sufficiently stronger than the pilot signal in the current coverage area, the user device may then engage in control channel signaling with the RAN to arrange for a handoff from the current coverage area to the adjacent coverage area.
Under some communications protocols, such as 1xEV-DO, data transmitted on the forward link (from the BTS to the AT) is defined in terms of frames. These frames are divided into a number of time slots, each slot being approximately 1.667 ms in length. The AT may regularly measure the frame error rate (FER) on the forward link. The FER is the ratio of the number of bad frames to the total number of frames received by the AT for a period of time. The AT may periodically report the FER measurements to the BSC using Power Measurement Report messages. In turn, the BSC may adjust the BTS's forward power based on the FER reported by the AT. If the FER is high, the BSC may increase the BTS's forward power, to improve call fidelity, for instance. If the FER is low, the BSC may decrease the BTS's forward power, so as to direct resources elsewhere.
Wireless service providers typically require that users pay a fee in order to receive service. In some instances, users are allotted a certain amount of minutes (or a certain amount of data) per month, and the wireless service provider monitors the user's usage.